USB_MAKE_PATH(9)					  Host-Side Data Types and Macro					  USB_MAKE_PATH(9)

NAME

       usb_make_path - returns stable device path in the usb tree

SYNOPSIS

       int usb_make_path(struct usb_device * dev, char * buf, size_t size);

ARGUMENTS

       dev
	   the device whose path is being constructed

       buf
	   where to put the string

       size
	   how big is "buf"?

DESCRIPTION

       Returns length of the string (> 0) or negative if size was too small.

       This identifier is intended to be "stable", reflecting physical paths in hardware such as physical bus addresses for host controllers or
       ports on USB hubs. That makes it stay the same until systems are physically reconfigured, by re-cabling a tree of USB devices or by moving
       USB host controllers. Adding and removing devices, including virtual root hubs in host controller driver modules, does not change these
       path identifers; neither does rebooting or re-enumerating. These are more useful identifiers than changeable ("unstable") ones like bus
       numbers or device addresses.

       With a partial exception for devices connected to USB 2.0 root hubs, these identifiers are also predictable. So long as the device tree
       isn't changed, plugging any USB device into a given hub port always gives it the same path. Because of the use of "companion" controllers,
       devices connected to ports on USB 2.0 root hubs (EHCI host controllers) will get one path ID if they are high speed, and a different one if
       they are full or low speed.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							  USB_MAKE_PATH(9)